Fractional frequency reuse in heterogeneous networks

ABSTRACT

A base station node (BS) of a heterogeneous radio access network comprises a terminal locator ( 34 ) and a scheduler ( 36 ). The terminal locator ( 34 ) obtains an indication of location of a wireless terminal ( 30 ) in a cell served by the base station (BS), e.g., whether the wireless terminal ( 30 ) is in a center region (M) or an edge region (E) for the cell served by the base station node (BS). The scheduler ( 36 ) uses the indication of location to assign to the wireless terminal ( 30 ) a frequency of a frequency bandwidth usable by the heterogeneous radio access network. The scheduler ( 36 ) assigns a frequency from a partitioned portion of the frequency bandwidth if the cell served by the base station node is a micro cell and the wireless terminal is in an edge region of a micro cell. The scheduler ( 36 ) also assigns a frequency of the frequency bandwidth if the cell served by the base station node is a micro cell and the wireless terminal is in a center portion of the micro cell.

This application is a continuation-in-part of PCT applicationPCT/EP2010/007699, filed Dec. 15, 2010, entitled “Technique forInter-Cell Interference Coordination in a Heterogeneous CommunicationNetwork”, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention pertains to telecommunications, and particularly toresource allocation in telecommunications networks.

BACKGROUND

In a typical cellular radio system, wireless terminals (also known asmobile stations and/or user equipment units (UEs)) communicate via aradio access network (RAN) to one or more core networks. The radioaccess network (RAN) covers a geographical area which is divided intocell areas, with each cell area being served by a base station node,e.g., a radio base station (RBS), which in some networks may also becalled, for example, a “NodeB” (UMTS) or “eNodeB” (LTE). A cell is ageographical area where radio coverage is provided by the radio basestation equipment at a base station site. Each cell is identified by anidentity within the local radio area, which is broadcast in the cell.Another identity identifying the cell uniquely in the whole mobilenetwork is also broadcasted in the cell. The base stations communicateover the air interface operating on radio frequencies with the userequipment units (UE) within range of the base stations.

In some versions of the radio access network, several base stations aretypically connected (e.g., by landlines or microwave) to a controllernode (such as a radio network controller (RNC) or a base stationcontroller (BSC)) which supervises and coordinates various activities ofthe plural base stations connected thereto. The radio networkcontrollers are typically connected to one or more core networks.

The Universal Mobile Telecommunications System (UMTS) is a thirdgeneration mobile communication system, which evolved from the secondgeneration (2G) Global System for Mobile Communications (GSM). UTRAN isessentially a radio access network using wideband code division multipleaccess for user equipment units (UEs). In a forum known as the ThirdGeneration Partnership Project (3GPP), telecommunications supplierspropose and agree upon standards for third generation networks and UTRANspecifically, and investigate enhanced data rate and radio capacity.Specifications for the Evolved Packet System (EPS) have completed withinthe 3^(rd) Generation Partnership Project (3GPP) and this work continuesin the coming 3GPP releases. The EPS comprises the Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) (also known as the Long TermEvolution (LTE) radio access) and the Evolved Packet Core (EPC) (alsoknown as System Architecture Evolution (SAE) core network). E-UTRAN/LTEis a variant of a 3GPP radio access technology wherein the radio basestation nodes are directly connected to the EPC core network rather thanto radio network controller (RNC) nodes. In general, in E-UTRAN/LTE thefunctions of a radio network controller (RNC) node are distributedbetween the radio base stations nodes (eNodeB's in LTE) and the corenetwork. As such, the radio access network (RAN) of an EPS system has anessentially “flat” architecture comprising radio base station nodeswithout reporting to radio network controller (RNC) nodes.

In a homogeneous deployment with a single cell layer, the transceiverdevices that are sensitive to interference are usually also the onesthat cause high interference to transceiver devices in adjacent cells.In the uplink (UL) the reason for this concurrence is the following: asensitive transceiver device is one that has high pathloss to theserving base station, and therefore the power received by the servingbase station is low, in particular if the transceiver device reaches itspower limit. A transceiver device with high pathloss is typically at thecell border (commonly called cell-edge transceiver device), which iswhere it is also closest to adjacent cells (and adjacent base stations).For these adjacent cells the transceiver device (especially whenoperating at its power limit) is typically a strong interferer.

The growing demands on mobile networks to support data applications athigher throughputs and spectral efficiencies has driven the need todevelop Orthogonal Frequency Division Multiplexing (OFDM)-based 4^(th)generation (4G) networks including for 3GPP Long Term Evolution (LTE). Akey objective with respect to deployment of OFDM 4G networks is toutilize a frequency re-use of one (denoted by N=1), or as close to N=1re-use as is practical. A frequency re-use of N=1 implies that the basestations in cells transmit on all available time-frequency resourcesblocks (RBs) simultaneously. Due to transmit power limitations in mobileterminals, the need for higher throughputs in 4G networks, especiallynear the cell edge, combined with the constraint on the uplink linkbudget will necessitate the need for smaller cell sizes than istypically deployed for present 2^(nd) generation (2G) and 3^(rd)generation (3G) cellular systems.

The use of smaller cells sizes can be deployed in a traditionalhomogenous cell splitting approach or in a more ad hoc heterogeneousapproach in which pico cells or relay nodes are overlaid on an existingmacro cellular network. For both a homogeneous and heterogeneousapproach, the resulting interference limited system for N=1 deploymentwill not achieve the full potential capacity that the LTE standard cansupport without the implementation at the base station and mobileterminal of one or more viable interference mitigation and orcancellation techniques.

Interference cancellation and mitigation techniques have beeninvestigated and deployed with varying degrees of success in terrestrialmobile networks for over twenty years. Traditional approaches tointerference mitigation between transmitted signals have focused oneither ensuring orthogonality between transmitted signals in time,frequency as well as spatially or by actively removing and cancellinginterfering signals from the desired signal if orthogonality between thedesired signal and potential interferers cannot be achieved. In early 2Gcellular systems such orthogonality was achieved primarily throughstatic pre-planned allocations of radio resources.

3G systems introduced interference cancellation techniques based mostlyon a combination of blind information gathering at a base station suchas spectrum usage monitoring and coarse exchange of interferenceindicators such as the Rise over Thermal (RoT) indicator employed in the3GPP2 1xEV-DO standard. Typically interfering signals have beenestimated using blind detection and their estimates subtracted from thedesired signals.

From a link perspective the downlink (DL) allows for a more tractableanalysis since if the desired mobile terminal location is known, thedistances to all potential interfering base stations can be easilydetermined based on the network geometry and hence a probabilistic basedestimate of the signal-to-interference-plus-noise (SINR) can becalculated based on the channel fading conditions for the desired signaland the interfering signals. In addition to additive white Gaussiannoise (AWGN), both the desired signal and interfering signals willexperience shadowing which typically is log-normally distributed.

Analysis of the uplink (UL) interference requires knowledge of not onlythe location of the desired mobile terminal under consideration, butalso the relative locations of all potential interfering mobileterminals, for which both the locations of the interfering terminals,the number of potential terminals as well as their spatial velocity willbe random variables.

In cellular networks it is a well known problem that, in medium to heavyloading, the network becomes interference limited which can result innegative signal-to-interference-plus-noise (SINR) ratios, particularlyfor cell edge users.

The challenge with deploying a static N=1 frequency re-use OFDM systemin an interference limited environment is that for a fully loadeddeployment, significant regions of coverage will experience negativeSINR levels resulting in gaps in the deployed coverage, irrespective ofthe inter-cell distance. In an interference limited system it is notuncommon for on the order of 15% of users to experience negative SINR,with some users experiencing negative SINR levels of −10 to −15 dB. Itshould be noted that in a fully loaded interference limited cellulardeployment the severity of the SINR degradation will be highly dependenton the average path loss exponent. For a cellular deployment with afixed inter-cell distance, high path loss propagation environments withpath loss exponents up to a 5^(th) or 6^(th) order will experience lessoverall interference than deployments with lower path loss exponents,since potential interfering signals from neighboring cells will be moregreatly attenuated in the former case. Even though there will besignificant SINR variation depending on the propagation environment, inorder to robustly deploy an LTE OFDM system one will have to mitigatethe inevitable negative SINR coverage regions that will exist.

Fractional frequency re-use (FFR) is one approach that can be staticallyor adaptively employed in heterogeneous cellular network deployments toimprove the overall geometry and SINR levels, particularly for cell edgeusers. However this gain in SINR is typically at a cost of a decrease inoverall aggregate cell throughput and spectral efficiency. For example,overall throughput is reduced to about 70% of an N=1 deployment if N=⅓FFR is employed.

Use of pico-cell or relay node overlays on existing macro cellulardeployments can also be employed to improve cell coverage as well asincrease cell edge or overall cell throughput. However macro/pico-cellheterogeneous deployments suffer from a number of potential problems. InLTE Release 8, cell selection between macro-cell base stations andpico-cell base stations will typically be based on use of referencesymbol received power (RSRP). With such an approach, macro-cell UEs nearthe macro cell edge will typically be transmitting with high power andcan cause a high level of interference to nearby pico-cell basestations. On the downlink (DL) if the UE has open access to either themacro or pico base stations, the UE can connect to the best link.However, at the border between the macro and pico cells thesignal-to-interference (SIR) level can be low. In such a situation,inter-cell interference-coordination approaches can be beneficial.However if access to the pico or femto-cells of the heterogeneousnetwork is restricted or closed (e.g., closed subscriber groups orCSGs), the femto-cell base stations can cause a high level ofinterference to nearby macro UEs that cannot handover to the femto basestations.

A second possible approach for cell selection between macro and picobase stations is to employ a path gain approach which is optimal forload balancing. With such an approach the UL signal strength willgenerally be robust, however the SIR at the macro-pico cell borders maybe low. With respect to the DL, high interference may be experienced bythe pico UEs from the macro base station transmissions for both thecontrol and data channels. Furthermore, for a CSG scenario, macro UEsclose to the pico base station can only connect to the macro basestation and will be a source of high interference to the pico basestation for UL transmissions.

SUMMARY

In one of its aspects the technology disclosed herein concerns variousexample embodiments of base station nodes, e.g., base stations, of aheterogeneous radio access network. The heterogeneous radio accessnetwork comprises a macro layer (which includes at least one macro cellserved by a macro base station) and a micro layer (which includes atleast one micro cell served by a micro base station). Some exampleembodiments of base station nodes are macro base stations serving macrocells; other example embodiments of base station nodes are micro basestations serving micro cells.

In an example embodiment the base station comprises a terminal locatorand a scheduler. The terminal locator is configured to obtain anindication of location of a wireless terminal in a cell served by thebase station. For example, the terminal location may determine whetherthe wireless terminal is in a center region or an edge region of thecell served by the base station node.

The scheduler is configured to use the indication of location to assignto the wireless terminal a frequency of the frequency bandwidth usableby the heterogeneous radio access network. The scheduler, known as alocation-influenced partitioning scheduler, is particularly configuredto assign a frequency from a partitioned portion of the frequencybandwidth if the cell served by the base station node is a micro celland the wireless terminal is in an edge region of a micro cell. Thescheduler is also configured to assign a frequency of the frequencybandwidth if the cell served by the base station node is a micro celland the wireless terminal is in a center portion of the micro cell. Thefrequency assignment to a wireless terminal that is in a center portionof a cell may be by different criteria than that of a wireless terminalin an edge portion of the cell. For example, the micro base station mayassign a frequency of the frequency bandwidth without regard to thepartitioned portion (e.g., at any suitable frequency in the frequencybandwidth without constraint of the partitioned portion) if the wirelessterminal is in a center portion of the micro cell.

In an example embodiment, if the cell served by the base station node isa macro cell the scheduler is further configured to assign a frequencyof the frequency bandwidth if the wireless terminal is served by themacro cell and is in a center portion of the macro cell or does notsubstantially interfere with a micro cell. The frequency assignment to awireless terminal that is in a center portion of a cell may be bydifferent criteria than that of a wireless terminal in an edge portionof the cell. For example, the scheduler may be further configured toassign a frequency of the frequency bandwidth without regard to thepartitioned portion if the wireless terminal is served by the macro celland is in a center portion of the macro cell or does not substantiallyinterfere with a micro cell.

As used herein, a “partitioned portion” is less than the entirefrequency bandwidth usable by the heterogeneous radio access network.Typically the frequency bandwidth used by the heterogeneous radio accessnetwork is divided into plural partitions, e.g., at least a firstpartition and a second partition. Thus, a partitioned portion may be asubset of the frequency bandwidth usable by the heterogeneous radioaccess network, and may comprise one of plural partitions of thefrequency bandwidth. Being assigned a frequency from a partitionedportion means that a wireless terminal is not eligible to have afrequency assignment from all frequencies of the bandwidth usable by theheterogeneous radio access network.

As mentioned above, in some example embodiments the base station nodesare micro base stations serving micro cells. In such exampleembodiments, the heterogeneous radio access network comprises pluralmacro cells and plural micro cells within each of the plural macrocells, and the frequency bandwidth used by the heterogeneous radioaccess network is divided into plural partitions.

In some example embodiments of micro base station nodes the scheduler isconfigured to assign a frequency from the second partition if thewireless terminal is in an edge region of a micro cell served by themicro base station node.

In some example embodiments of micro base station nodes selected one ofthe plural partitions is a different partition than that which is usedby a micro base station node within the macro cell to assign a frequencyto any wireless terminal within the micro base station node. In anexample implementation the selected one of the plural partitions is asame partition that is used by a micro base station node within anothermacro cell to assign a frequency to a wireless terminal in an edgeregion of the micro base station node which is in the another macrocell.

In some example embodiments of micro base station nodes the scheduler isfurther configured to assign the frequency from a selected one of pluralpartitions of the frequency bandwidth, the selected one of the pluralpartitions being a same partition which is used, by another base stationnode serving another micro cell in a same macro cell, to assign afrequency to another wireless terminal in an edge region of the anothermicro cell, but the selected one of the plural partitions beingdifferent from another partition which is used, by yet another basestation node serving another micro cell in another macro cell which isadjacent to the macro cell, to assign a frequency to yet anotherwireless terminal in an edge region of the yet another micro cell.

In some example embodiments of micro base station nodes the scheduler isfurther configured to assign the frequency from a selected one of pluralpartitions of the frequency bandwidth, the selected one of the pluralpartitions being a different partition than that which is used, byanother base station node serving another micro cell in a same macrocell, to assign a frequency to another wireless terminal in an edgeregion of the another micro cell.

In some example embodiments of micro base station nodes the pluralpartitions are divided into plural sub-partitions. A first partition isassociated with the plural macro cells and a second partition isassociated with the plural micro cells. A first sub-partition of thesecond partition is primarily for micro cells in a first macro cell anda second sub-partition of the second partition is primarily for microcells in a second macro cell. Alternatively the first sub-partition ofthe second partition may be primarily for a first micro cell in thefirst macro cell and the second sub-partition may be for a second microcell (or other micro cells) in the first macro cell. The base stationnode serves a particular micro cell comprising the plural micro cells.The scheduler is further configured to assign to the wireless terminal afrequency selected from a selected sub-partition of the second partitionif the wireless terminal is in an edge region of the particular microcell. In an example implementation, the selected sub-partition of thesecond partition is associated with the macro cell in which theparticular micro cell is located.

In some example embodiments the base station nodes are macro basestations serving macro cells. In such example embodiments, theheterogeneous radio access network comprises plural macro cells andplural micro cells within each of the plural macro cells, and thefrequency bandwidth used by the heterogeneous radio access network isdivided into plural partitions.

The scheduler is configured to assign a frequency of the frequencybandwidth if the wireless terminal is in a center portion of the cellserved by the base station node or does not substantially interfere witha micro cell. The frequency assignment to a wireless terminal that is ina center portion of a cell may be by different criteria than that of awireless terminal in an edge portion of the cell. For example, in someexample embodiments of macro base station nodes, the scheduler isconfigured to assign a frequency of the frequency bandwidth withoutregard to the partitioned portion if the wireless terminal is in acenter portion of the cell served by the base station node or does notsubstantially interfere with a micro cell.

In some example embodiments of micro base station nodes the scheduler isconfigured to assign a frequency from a first partition if the wirelessterminal is in an edge region of a macro cell served by the macro basestation node.

In some example embodiments of micro base station nodes the scheduler isfurther configured to assign a frequency from the a selected one ofplural partitions of the frequency bandwidth if the wireless terminal isin an edge region of the cell served by the macro base station node, theselected one of the plural partitions being a different partition thanthat which is used by another base station node serving an adjacentmacro cell to assign a frequency to another wireless terminal in an edgeregion of the adjacent macro cell. In an example implementation, theselected one of the plural partitions is a different partition than thatwhich is used by a micro base station node within the macro cell toassign a frequency to any wireless terminal within the micro basestation node. In another example implementation, the selected one of theplural partitions is a same partition that is used by a micro basestation node within another macro cell to assign a frequency to awireless terminal in an edge region of the micro base station node whichis in the other macro cell.

Some example embodiments of micro base station nodes, are two stageembodiments. In the two stage embodiments the plural partitions aredivided into plural sub-partitions. A first partition is associated withone or more macro cells and a second partition is primarily associatedwith the plural micro cells. The macro base station node serves aparticular macro cell comprising the plural macro cells.

In an example two stage embodiment of a macro base station the scheduleris further configured to assign to the wireless terminal a frequency ofa selected one of the sub-partitions of the first partition if thewireless terminal is in an edge region of the particular macro celland/or substantially interferes with a cell other than the particularmacro cell. In an example implementation, the selected one of thesub-partitions of the first partition is a sub-partition associated withthe particular macro cell.

In another example two stage embodiment of a macro base station a firstpartition is associated with the plural macro cells and a secondpartition is primarily associated with the plural micro cells. The basestation node serves a particular macro cell comprising the plural macrocells. The scheduler is further configured to assign to the wirelessterminal a frequency of the frequency bandwidth usable by theheterogeneous radio access network if the wireless terminal does notsubstantially interfere with a cell other than the particular macrocell. For example, the scheduler 36 may assign to the wireless terminala frequency of the frequency bandwidth by different critiera, e.g.,without regard to the partitioned portion.

In another example two stage embodiment of a macro base station a firstpartition is associated with the plural macro cells and a secondpartition is associated with the plural micro cells. The base stationnode serves a particular macro cell comprising the plural macro cells.The scheduler is further configured to assign to the wireless terminal afrequency of the second partition if the wireless terminal substantiallyinterferes with a macro cell other than the particular macro cell anddoes not substantially interfere with a micro cell. In an exampleimplementation, the scheduler is further configured to assign to thewireless terminal a frequency of a selected one of the sub-partitions ofthe second partition, and wherein the selected one of the sub-partitionsof the second partition is associated with the particular macro cell.

In another of its aspects the technology disclosed herein concerns amethod of operating a heterogeneous radio access network. Theheterogeneous radio access network comprises a macro layer including atleast one macro cell served by a macro base station and a micro layercomprising at least one micro cell served by a micro base station. In anexample embodiment and mode the method comprises dividing a frequencybandwidth usable by the heterogeneous radio access network into apartitioned portion which is less than the entire bandwidth. The methodfurther comprises assigning a frequency of the partitioned portion to awireless terminal in an edge region of the micro cell; and assigning afrequency of the frequency bandwidth to a wireless terminal which is ina center region of the micro cell. The frequency assignment to awireless terminal is in a center portion of a cell may be by differentcriteria than that of a wireless terminal in an edge portion of thecell. For example, the micro base station may assign a frequency of thefrequency bandwidth without regard to the partitioned portion (e.g., atany suitable frequency in the frequency bandwidth without constraint ofthe partitioned portion) if the wireless terminal is in a center portionof the micro cell.

In an example embodiment and mode the method further comprisesassigning, e.g., by different critiera (e.g., without regard to thepartitioned portion), a frequency of the frequency bandwidth to awireless terminal which is in a center region of the macro cell.

In an example embodiment and mode the method further comprisesdetermining whether the wireless terminal is in the center region or theedge region for the micro cell.

In an example embodiment and mode the method further comprises dividingthe frequency bandwidth usable by the heterogeneous radio access networkinto plural partitioned portions (each of which is less than the entirebandwidth), and assigning frequencies from the partitioned portions towireless terminals in an edge region of the macro cell and wirelessterminals in an edge region of the micro cell.

In an example implementation, the method further comprises: dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions; assigning a frequency from a first partition towireless terminals in an edge region of the macro cell; and, assigning afrequency from a second partition to wireless terminals in a edge regionof the micro cell.

In an example embodiment and mode, the method further comprises:dividing the frequency bandwidth usable by the heterogeneous radioaccess network into plural partitions; assigning a frequency from afirst partition to wireless terminals in the edge region of a firstmacro cell; assigning a frequency from a second partition to a wirelessterminal in the edge region of a second macro cell; and, assigning afrequency from a third partition to a wireless terminal in the edgeregion of a micro cell.

In an example implementation the method further comprises assigning thefrequency from the third partition to the wireless terminal in the edgeregion of a micro cell regardless of whether the micro cell is in thefirst macro cell or the second macro cell.

In an example embodiment and mode the method further comprises: dividingthe frequency bandwidth usable by the heterogeneous radio access networkinto plural partitions; assigning a frequency from a first partition toa wireless terminal in an edge region of a first macro cell; assigning afrequency from a second partition to a wireless terminal in an edgeregion of a second macro cell; assigning a frequency from a thirdpartition to a wireless terminal in an edge region of a first micro cellwithin the first macro cell; and, assigning a frequency from a fourthpartition to a wireless terminal in an edge region of a second microcell within the first macro cell.

In an example embodiment and mode, the method further comprises:assigning a frequency from the third partition to a wireless terminal inan edge region of a first micro cell within the second macro cell; andassigning a frequency from the fourth partition to a wireless terminalin an edge region of a second micro cell within the second macro cell.

In an example embodiment and mode the method further comprises: dividingthe frequency bandwidth usable by the heterogeneous radio access networkinto plural partitions; assigning a frequency of a first partition towireless terminals in an edge region of the plural micro cells within afirst macro cell; and assigning a frequency of a second partition towireless terminals in an edge region of the plural micro cells within asecond macro cell.

In an example implementation, the method further comprises assigning afrequency of the frequency bandwidth to a wireless terminal which is inany of the plural macro cells or in the center region of any of theplural micro cells. Such assignment may be without regard to the pluralpartitioned portion.

In an example embodiment and mode the method further comprises: dividingthe frequency bandwidth usable by the heterogeneous radio access networkinto plural partitions; assigning a frequency of a first partition to awireless terminal in an edge region of a first micro cell within a firstmacro cell; and, assigning a frequency of a second partition to awireless terminal in an edge region of a second micro cell within thefirst macro cell.

In an example embodiment and mode, the method further comprises:assigning a frequency of the first partition to a wireless terminal inan edge region of a first micro cell within a second macro cell; and,assigning a frequency of the second partition to a wireless terminal inan edge region of a second micro cell within the second macro cell.

Some example embodiments and modes involve multiple (e.g., two) stagesof partitioning. In an example embodiment and mode the method furthercomprises: dividing the frequency bandwidth usable by the heterogeneousradio access network into plural partitions including a first partitionand a second partition; dividing the plural partitions into pluralsub-partitions; assigning a frequency of a second partition to awireless terminal in an edge region of one of the plural micro cells by:assigning a frequency of a first sub-partition of the second partitionif the wireless terminal is in an edge region of a micro cell in thefirst macro cell; and assigning a frequency of a second sub-partition ofthe second partition if the wireless terminal is in an edge region of amicro cell in the second macro cell.

In an example embodiment and mode the method further comprises assigninga frequency of a first partition to a wireless terminal in an edgeregion of one of the plural macro cells by: assigning a frequency of afirst sub-partition of the first partition if the wireless terminal isin an edge region of a first macro cell; and assigning a frequency of asecond sub-partition of the first partition if the wireless terminal isin an edge region of a second macro cell.

In an example embodiment and mode the method further comprises assigninga frequency of a first partition to a wireless terminal in one of theplural macro cells by: assigning a frequency of a first sub-partition ofthe first partition if the wireless terminal is in an edge region of afirst macro cell and interferes with any micro base station node; andassigning a frequency of a second sub-partition of the first partitionif the wireless terminal is in a second macro cell and interferes withany micro base station node.

In an example embodiment and mode the method further comprises:assigning a frequency of the second partition to a wireless terminal inone of the plural macro cells if the wireless terminal is in a macrocell and does not substantially interfere with any micro base stationnode.

In an example embodiment and mode the method further comprises assigninga frequency of to the wireless terminal in one of the plural macro cellsby: assigning a frequency of a first sub-partition of the secondpartition if the wireless terminal is in an edge region of a first macrocell and does not substantially interfere with any micro base stationnode; and assigning a frequency of a second sub-partition of the secondpartition if the wireless terminal is in a second macro cell and doesnot substantially interfere with any micro base station node.

In an example embodiment and mode the frequency bandwidth the firstsub-partition of the first partition is separated from the firstsub-partition of the second partition by at least the secondsub-partition of the first partition.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments as illustrated in the accompanyingdrawings in which reference characters refer to the same partsthroughout the various views. The drawings are not necessarily to scale,emphasis instead being placed upon illustrating the principles of theinvention.

FIG. 1 is a diagrammatic view of portions of a heterogeneous radioaccess network which is simplified to illustrate a macro layer and amicro layer.

FIG. 2 is a diagrammatic view of portions of a heterogeneous radioaccess network showing, e.g., example placement of different types ofbase stations.

FIG. 3 is a diagrammatic view of portions of a heterogeneous radioaccess network showing comprising plural macro cells, each macro cellserving plural micro cells.

FIG. 3A is a diagrammatic view illustrating a partitioning into a first“prioritized” sub-band associated with one or more cells of a first celllayer and a second “prioritized” sub-band associated with one or morecells of a second cell layer.

FIG. 4 a diagrammatic view of portions of an example embodiment of ageneric base station node.

FIG. 5 is a diagrammatic view of portions of an example embodiment of ageneric wireless terminal.

FIG. 6 a diagrammatic view illustrating a center region M of a cell anda edge region E of a cell.

FIG. 7 is a flowchart illustrating representative, basic acts or stepsperformed in a generic mode of an example method of the technologydisclosed herein.

7A is a flowchart illustrating representative, basic acts or stepsperformed in a modified mode of the basic method of FIG. 7.

FIG. 7B is a flowchart illustrating representative, basic acts or stepsperformed in a more detailed mode of the basic method of FIG. 7.

FIG. 7C is a flowchart illustrating representative, basic acts or stepsperformed in another more detailed mode of the basic method of FIG. 7.

FIG. 8 is a diagrammatic view depicting downloading of a partition planfrom a central or management node to base station nodes of aheterogeneous radio access network.

FIG. 9 is a diagrammatic view depicting loading of a partition plan intobase station nodes of a heterogeneous radio access network.

FIG. 10A, FIG. 11A, FIG. 12A, FIG. 13A, FIG. 14A are diagrammatic viewsillustrating example embodiments and modes of a resource allocationstrategies according to the technology disclosed herein.

FIG. 10B, FIG. 11B, FIG. 12B, FIG. 13B, and FIG. 14B are flowchartsillustrating representative, basic acts or steps performed in methods ofoperating a heterogeneous radio access network in accordance with therespective strategies of FIG. 10A, FIG. 11A, FIG. 12A, FIG. 13A, andFIG. 14.

FIG. 11C, FIG. 12C, FIG. 13C, and FIG. 14C are flowcharts illustratingrepresentative, basic acts or steps performed in alternate methods ofoperating a heterogeneous radio access network in accordance with therespective strategies of FIG. 11A, FIG. 12A, FIG. 13A, and FIG. 14A.

FIG. 15 is a diagrammatic view illustrating an example embodiment andmode of a sub-partitioning resource allocation strategy according to thetechnology disclosed herein.

FIG. 15A is a diagrammatic view of portions of a heterogeneous radioaccess network showing a hatched region wherein macro wireless terminalsof a macro base station potentially strongly interfere with a microcell.

FIG. 16 is a diagrammatic view illustrating another example embodimentand mode of a sub-partitioning resource allocation strategy according tothe technology disclosed herein.

FIG. 16A is a diagrammatic view further illustrating the embodiment ofFIG. 16.

FIG. 17 and FIG. 17A-FIG. 17D are flowcharts illustratingrepresentative, basic acts or steps performed in methods of operating aheterogeneous radio access network in accordance with varioussub-partitioned embodiments and/or modes.

FIG. 18 a diagrammatic view of portions of another example embodiment ofa base station node, including a platform implementation.

FIG. 19 a diagrammatic view of portions of another example embodiment ofa wireless terminal, including a platform implementation.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particulararchitectures, interfaces, techniques, etc. in order to provide athorough understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention may bepracticed in other embodiments that depart from these specific details.That is, those skilled in the art will be able to devise variousarrangements which, although not explicitly described or shown herein,embody the principles of the invention and are included within itsspirit and scope. In some instances, detailed descriptions of well-knowndevices, circuits, and methods are omitted so as not to obscure thedescription of the present invention with unnecessary detail. Allstatements herein reciting principles, aspects, and embodiments of theinvention, as well as specific examples thereof, are intended toencompass both structural and functional equivalents thereof.Additionally, it is intended that such equivalents include bothcurrently known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure.

Thus, for example, it will be appreciated by those skilled in the artthat block diagrams herein can represent conceptual views ofillustrative circuitry or other functional units embodying theprinciples of the technology. Similarly, it will be appreciated that anyflow charts, state transition diagrams, pseudocode, and the likerepresent various processes which may be substantially represented incomputer readable medium and so executed by a computer or processor,whether or not such computer or processor is explicitly shown.

The functions of the various elements including functional blocks,including but not limited to those labeled or described as “computer”,“processor” or “controller”, may be provided through the use of hardwaresuch as circuit hardware and/or hardware capable of executing softwarein the form of coded instructions stored on computer readable medium.Thus, such functions and illustrated functional blocks are to beunderstood as being either hardware-implemented and/orcomputer-implemented, and thus machine-implemented.

In terms of hardware implementation, the functional blocks may includeor encompass, without limitation, digital signal processor (DSP)hardware, reduced instruction set processor, hardware (e.g., digital oranalog) circuitry including but not limited to application specificintegrated circuit(s) [ASIC], and (where appropriate) state machinescapable of performing such functions.

In terms of computer implementation, a computer is generally understoodto comprise one or more processors or one or more controllers, and theterms computer and processor and controller may be employedinterchangeably herein. When provided by a computer or processor orcontroller, the functions may be provided by a single dedicated computeror processor or controller, by a single shared computer or processor orcontroller, or by a plurality of individual computers or processors orcontrollers, some of which may be shared or distributed. Moreover, useof the term “processor” or “controller” shall also be construed to referto other hardware capable of performing such functions and/or executingsoftware, such as the example hardware recited above.

FIG. 1 shows portions of a heterogeneous radio access network 20, andparticularly macro cell 22 which is served by macro base station 24. Oneor more micro base stations 26 are situated within or proximate macrocell 22. Each micro base station serves a corresponding micro cell 28.The macro and micro base stations communicate over an air or radiointerface with one or more wireless terminals, also known as userequipment units (UEs). One such representative wireless terminal (UE) 30is shown and arbitrarily positioned in FIG. 1.

As used herein, the terminology “micro base station” is to be understoodas broadly encompassing any type of station which operates over a radioor air interface on both downlink (DL) and uplink (UL) and has extent oftransmission that is less than (e.g., in geographic range or power) orsubordinate to (e.g., delegated from/by) a macro base station. Incorresponding fashion the terminology “micro cell” refers to anycellular territory or coverage area served by such broadly defined microbase station. In other words, a macro base station has at least one ofhigher nominal transmit power and larger coverage area than a micro basestation. Examples of types of cells and base stations encompassed by theterminology “micro cell” and “micro base station” are illustrated inFIG. 2 as including pico cells and pico base stations, femto cells(which can exist in a femto cluster) and femto base stations, and relaybase stations. Macro base stations are typically separated by distanceson the order of kilometers, and thus the radii of macro cells is also onthe order of kilometers. On the other hand, micro base stations aretypically separated by distances on the order of a few hundred meters(e.g., 100 m-200 m, and in some instances 500 m), and thus the radii ofmicro cells is also on the order of a few hundred meters.

As will subsequently become more fully appreciated, FIG. 1 and FIG. 2show only one macro cell 22 of heterogeneous radio access network 20.Typically a heterogeneous radio access network comprises plural (e.g.,scores of) macro cells. Further, in some heterogeneous radio accessnetworks the operation of the macro base stations for the macro cellsand micro base stations for the micro cells may be coordinated,particularly in a Coordinated Multipoint (CoMP) system. In CoMParchitecture a collection of cells (e.g., sub-cells) may be connected toa central node that coordinates the transmission/reception of usersignals to mitigate interference among the smaller sub-cells. CoMParchitecture is understood with reference to, e.g., U.S. patentapplication Ser. No. 12/563,589, entitled “Inter-Cell InterferenceMitigation”, also published as United States Patent Publication US2010/0261493, which is incorporated herein by reference in its entirety.

As mentioned previously, a “wireless terminal” such as wireless terminal(UE) 30 encompasses mobile stations or user equipment units (UE) such asmobile telephones (“cellular” telephones) and laptops with wirelesscapability, e.g., mobile termination, and thus can be, for example,portable, pocket, hand-held, computer-included, or car-mounted mobiledevices which communicate voice and/or data with radio access network.In some example embodiments a wireless terminal need not be mobile butcan instead be fixed.

Information is typically transmitted over the air interface between basestations and wireless terminal in frames. In fact, in some radio accesstechnologies a frame typically comprises plural subframes, with each ofthe subframes being formatted similarly and in a manner understood byboth the base station and the wireless terminals. The frames andsubframes are formatted so that the macro and micro base stations, onthe one hand, and the wireless terminals 30, on the other hand, knowwhat type of information to expect in different portions of fields ofthe frame/subframe. In some radio access technologies, a subframe isconceptualized as comprising a two dimensional array or “resource grid”of resource elements (RE), the resource elements being arranged insymbol order along a first (horizontal) direction (defined, e.g., bytime [time division]) and according to frequency subcarrier along asecond (vertical) direction (defined, e.g., by frequency [frequencydivision]). With respect to the first or direction the symbols may begrouped into slots, e.g., six or seven symbols may comprise a slot ofthe subframe, with the subframe comprising plural (e.g., two) slots. Atleast some sets of resource elements of the subframe are generallyallocated to serve as “channels”, with some of the channels being usedfor transmission of control information while other channels are usedfor transmission of user data. Moreover, in some radio accesstechnologies some channels of the subframe are allocated fortransmission in a downlink (DL) [in a direction from a base station to awireless terminal] while other channels of the subframe may be allocatedfor transmission in an uplink (e.g., in a direction from a wirelessterminal to a base station).

In a manner to comprehend and encompass all the foregoing, FIG. 1illustrates a transmission of subframe 32 over the air interface betweena base station and a wireless terminal. The terminology “subframe” asherein utilized is to be understood as encompassing any unit ofinformation of repetitive or pre-defined format, and therefore is to beunderstood as being applicable to, e.g., a frame as well as a subframe.In view of the heterogeneous nature of network 20 and the networks'inclusion of both macro and micro base stations, FIG. 1 furtherillustrates that radio transmissions in network 20 occur both at a macrolayer and a micro layer. In particularly, macro base station 24exchanges subframes with one or more wireless terminals in the macrolayer, while the micro base stations 26 exchange subframes with one ormore wireless terminals in the micro layer. The depiction in FIG. 1 ofthe stratification of the macro layer and the micro layer is simply forillustrating delineation of the two layers, and does not necessarilyimpose any geographical or territorial characteristics or restrictionswith respect to either layer.

FIG. 3 shows an example heterogeneous radio access network 20 comprisingplural macro cells, e.g., macro cell 22 ₁ through macro cell 22 ₃. Againit will be appreciated that a fewer or greater number of macro cells maybe included in the heterogeneous radio access network 20. Each macrocell is served by a corresponding macro base station, so that macro basestation 24 ₁ through 24 ₃ are shown for respective macro cell 22 ₁through macro cell 22 ₃. FIG. 3 further illustrates that two micro cellsare situated within each macro cell, e.g., micro cell 28 ₁₋₁ and microcell 28 ₁₋₂ within macro cell 22 ₁; micro cell 28 ₂₋₁ and micro cell 28₂₋₂ within macro cell 22 ₂; and, micro cell 28 ₃₋₁ and micro cell 28 ₃₋₂within macro cell 22 ₃. The general layout of the example heterogeneousradio access network 20 of FIG. 3 serves as a basic template forillustrating various resource assignment strategies of the technologydisclosed herein.

Further, it should be understood that the illustrations of FIG. 1, FIG.2, and FIG. 3 with only two macro cells and two micro base stations andtheir respective locations within or near the macro cell is notlimiting, since a macro cell could encompass one or more than two microcells and such micro cells may be diversely and non-uniformly arrangedfrom one macro cell to another, depending upon geographic utilizationand traffic need and conditions.

In one of its aspects the technology disclosed herein concerns variousexample embodiments of base station nodes of a heterogeneous radioaccess network. Such base station nodes, also referred to as “basestations”, are at times collectively and individually referred to in thedrawings as “BS”. As illustrated by FIG. 1, the heterogeneous radioaccess network 20 comprises a macro layer (which includes at least onemacro cell served by a macro base station) and a micro layer (whichincludes at least one micro cell served by a micro base station). Someexample embodiments of base station nodes described herein are macrobase stations serving macro cells; other example embodiments of basestation nodes described herein are micro base stations serving microcells.

FIG. 4 shows an example embodiment of a generic base station node BS.The generic depiction of the base station BS in FIG. 4 is forillustrating certain features and functionalities of the base stationwithout regard to whether the base station happens to be a macro basestation serving a macro base station 24 or a micro base station 26serving a micro cell 28. In other words, FIG. 4 shows units andfunctionalities that are both pertinent to the technology disclosedherein and common to both macro base stations and micro base stationsencompassed hereby. In the example of FIG. 4, base station BS comprisesterminal locator 34, scheduler 36, and communications interface 38. Thebase station BS typically includes other units and functionalities knownto the person skilled in the art.

As explained herein, terminal locator 34 of base station BS obtains anindication of location of a wireless terminal 30 in a cell served by thebase station. For example, the terminal location may determine whetherthe wireless terminal is in a center region or an edge region for thecell served by the base station node, as explained herein, e.g., withreference to FIG. 6.

The scheduler 36 of a base station BS has many functions, includingassignment of resources (e.g., resources of a resource grid) for use incommunication between the base station BS and the wireless terminals 30which are served by the base station BS. The scheduler 36 typicallyassigns resources for use both on a downlink (DL) from the base stationBS to a wireless terminal 30, as well as resources for use on the uplink(UL) from the wireless terminal (UE) 30 to the base station BS. Suchresources may include or be described by one or more frequencies (e.g.,subcarriers) and one or more time slots. As understood in the art, someof the resources may be assigned to or associated with particularchannels. Various channels may have different names or purposes inaccordance with different various conventions or standards. The variousconventions or standards typically define messages in which grants ofthe allocated resources are communicated to the wireless terminals.

In accordance with the technology disclosed herein, scheduler 36 usesthe indication of location (as determined by terminal locator 34) toassign, to the wireless terminal, a “frequency” of the frequencybandwidth usable by the heterogeneous radio access network. Asillustrated by numerous embodiments herein described, scheduler 36 (alsoknown as a location-conscious partitioned scheduler) is particularlyconfigured to assign a frequency from a partitioned portion of thefrequency bandwidth if the cell served by the base station node is amicro cell and the wireless terminal is in an edge region of a microcell. The scheduler 36 is also configured to assign a frequency of thefrequency bandwidth if the cell served by the base station node is amicro cell and the wireless terminal is in a center portion of the microcell. The frequency assignment to a wireless terminal is in a centerportion of a cell may be by different criteria than that of a wirelessterminal in an edge portion of the cell. For example, the micro basestation may assign a frequency of the frequency bandwidth without regardto the partitioned portion (e.g., at any suitable frequency in thefrequency bandwidth without constraint of the partitioned portion) ifthe wireless terminal is in a center portion of the micro cell.

The partitioned portion of the frequency bandwidth to which a scheduler36 assigns a wireless terminal is also herein known as the prioritizedsub-band for the cell served by the base station to which the schedulerbelongs. Therefore, by assigning cell-edge transceiver devices to itsprioritized sub-band, a serving base station both protects them frominterference and avoids causing too much interference to cell-edgetransceiver devices of adjacent cells that assign their sensitivetransceiver devices to the respective prioritized sub-bands as well.

The scheduler 36 is also configured to assign a frequency of thefrequency bandwidth if the cell served by the base station node is amacro cell and the wireless terminal is at least in a center portion ofthe macro cell or does not substantially interfere with a micro cell. Insome embodiments the scheduler 36 is configured to assign a frequency ofthe frequency bandwidth by different criteria than that used for an edgewireless terminal. For example, in some embodiments the scheduler 36 isconfigured to assign a frequency of the frequency bandwidth withoutregard to the partitioned portion if the cell served by the base stationnode is a macro cell and the wireless terminal is at least in a centerportion of the macro cell or does not substantially interfere with amicro cell.

As used herein a “frequency” of the frequency bandwidth usable by theheterogeneous radio access network and assigned by scheduler 36 may beone or more frequency carriers (e.g., sub-carriers or sub-band) or otherfrequency resource(s) that utilize or are described with reference to aradio frequency spectrum. The singular term “frequency” is employed onlyfor sake of simplification, it being understood that typically the“frequency” assigned refers to plural frequencies (e.g., subcarriers)which may or may not be consecutive frequencies in the frequencyspectrum. Resource blocks comprised of several subcarriers (12 for LTE)do not have to be consecutively assigned. However, subcarriers within aresource block all have to be consecutively employed.

As used herein, a “partition” or “partitioned portion” is less than theentire frequency bandwidth usable by the heterogeneous radio accessnetwork. In accordance with the technology disclosed herein thefrequency bandwidth used by the heterogeneous radio access network istypically divided into plural partitions, e.g., at least a firstpartition and a second partition. Thus, a partition or partitionedportion may be a subset (e.g., one or more frequencies or sub-carriers)of the frequency bandwidth usable by the heterogeneous radio accessnetwork, and may comprise one of plural partitions of the frequencybandwidth. Being assigned a frequency from a partitioned portion meansthat a wireless terminal is not eligible to have a frequency assignmentfrom all frequencies of the bandwidth usable by the heterogeneous radioaccess network. Thus, in the context of the LTE standard, for example, apartition or “partitioned portion” may be a plurality of subcarriers orresource blocks. A frequency or a “sub-band” may be any continuous ordiscontinuous spectral portion having well-defined boundaries and beingassociated with one or more cells (or one or more BSs). Associationsbetween sub-bands and cells or BSs may be statically determined or mayalternatively be dynamically defined.

It should also be understood that the “frequency” assigned by scheduler36 may be either for purposes of the downlink (DL) or the uplink (UL),although in some example scenarios illustrated herein the frequencyassigned by the scheduler 36 is primarily for the uplink (UL).

The communications interface 38 facilitates communication between thebase station BS and the wireless terminal (UE) 30 over a radio or airinterface. Such communication may employ the frame and/or sub-frame 32as before mentioned. The subframe itself is described by variousresources assigned by the scheduler 36. The communications interface 38may comprise or connect to one or plural antenna elements depending onthe type of technology utilized.

In some example embodiments a communication link is provided between amacro base station node 24 and a micro base station node 26.Specifically, an inter-processor communication link may be provided.This communication link permits exchange of information about therespective sub-bands associated with the macro cell and the micro cell.Additionally, sub-band negotiation procedures may be performed via thiscommunication link between the macro base station node and the microbase station node. Such communication between the macro base stationnode and the micro base station node may be via a communication link maybe based on the X2 interface as defined, for example, for LTE Release 8(see 3GPP TS 36.423, Evolved Universal Terrestrial Radio Access(E-UTRA), X2 application protocol (X2AP)). Specifically, any of theInformation Elements (IEs) exchanged over the X2 interface may be usedfor sub-band signalling purposes, including the Overload Indicator (OI)and the High Interference Indication (HII).

FIG. 5 shows an example embodiment of basic structure of a wirelessterminal (UE) 30. Among its other units and functionalities (known tothe person skilled in the art), wireless terminal (UE) 30 of FIG. 5comprises measurement unit 40; scheduler 42; and communicationsinterface 44. The measurement unit 40 performs measurements which arereported via communications interface 44 over the radio interface to thebase station BS. The measurements obtained by measurement unit 40 enablethe terminal locator 34 of the base station BS to determine the locationof wireless terminal 30, so that the terminal locator 34 can ascertainwhether the wireless terminal (UE) 30 is in a center region M or an edgeregion R of a cell served by the base station BS.

It was mentioned above that terminal locator 34 obtains an indication oflocation of a wireless terminal 30. As used herein “location” of awireless terminal refers to geographic location, e.g., whether thewireless terminal is in a center region or an edge region for the cellserved by the base station node. FIG. 6 illustrates a generic cell C asbeing divided into center or middle region M and edge region E. In FIG.6 (as in various other figures) the center region M of the cell C isshown by stippling (e.g., dotted texture). For the particular situationshown in FIG. 6 (but not necessarily in all other figures) the edgeregion E is depicted by horizontal hatching.

One or more metrics may be employed to determine whether a wirelessterminal (UE) 30 is in a center region M of a cell or an edge region Eof a cell. For example, a signal to interference/noise ratio (SINR) maybe evaluated to ascertain whether the wireless terminal (UE) 30 is in acenter region M of a cell or an edge region E of a cell. In this regard,a SINR value is measured by the measurement unit 40 and reported via thecommunications interface 44 from the wireless terminal (UE) 30 to thebase station BS. The terminal locator 34 of the base station BS receivesthe SINR value reported by the wireless terminal (UE) 30 and makes adetermination whether the reporting wireless terminal is in a centerregion M of the cell served by the base station or in an edge region Eof the cell served by the base station. A SINR value which is lower thana predetermined value or threshold may be considered by the terminallocator 34 of the base station BS to be indicative of the wirelessterminal being in the center region M of a cell, while conversely a SINRvalue exceeding the predetermined value or threshold may be indicativeof the wireless terminal being in the edge region E of a cell.

SINR is typically derived from a reference signal received power (RSRP)measurement and a received signal strength indicator (RSSI). Therefore awireless terminal may measure the reference signal received power (RSRP)to obtain an estimate of signal power, and then evaluate (e.g., measure)another metric such as received signal strength (RSSI) and look at totalreceived signal power, which may provide an estimate of interference.

Another metric may be path loss. In this regard, an estimate thedistance of the wireless terminal from the base station may be relatedto path loss based on timing delay between the wireless terminal and thereceived signal base station. Thus, one or more (e.g., a combination) ofthese metrics may be compared to a predetermined value or threshold toascertain whether the wireless terminal is in the center region M of acell or the edge region E of a cell.

Based on measurements performed, e.g., by measurement unit 40, awireless terminal (UE) 30 typically provides feedback regarding a cellfor which the wireless terminal (UE) 30 is receiving the best SINR. Ifnot already in that best cell, the network typically directs that ahandover (HO) be performed so that the wireless terminal is “handedover” to the best cell, so that the best cell can serve as the servingcell for the wireless terminal. The scheduling decisions (e.g., resourceallocations) for the wireless terminal (UE) 30 are made with respect tothe serving cell, e.g., by the base station of the serving cell.

Thus, a particular wireless terminal (UE) 30 may indicate when thewireless terminal believes that a handover (HO) should occur, but it isup to the network to make the handover (HO) or assignment and to aserving cell which the network believes is the strongest cell for thewireless terminal. The serving cell could be a macro cell or a microcell. Once assigned to a serving cell, the schedule of the serving cell(whether a macro cell or a micro cell) makes decisions as to whichresources are to be assigned.

The technology disclosed herein concerns how those decisions are madeand provides various techniques and strategies for allocating thefrequency resources for a heterogeneous radio access network. Asexplained herein, the techniques and strategies for allocating thefrequency resources depends on where the wireless terminal is in theserving cell, e.g., whether the wireless terminal is in a center regionM of the serving cell or the edge region E of the serving cell (see FIG.6). One basic concept of the technology disclosed herein is toincorporate the assignment of frequency resources between the macro andmicro base stations as part of a fractional frequency reuse scheme.

To implement FFR-based inter-cell interference coordination (ICIC) in aheterogeneously deployed cellular communication network comprising twoor more cell layers, continuous or discontinuous spectral resourcesavailable for UL transmissions are partitioned into at least twosub-bands. FIG. 3A illustrates such a partitioning into a first“prioritized” sub-band associated with one or more cells of a first celllayer (e.g., macro cell layer) and a second “prioritized” sub-bandassociated with one or more cells of a second cell layer (e.g., microcell layer). As becomes apparent from FIG. 3A, the two sub-bands aredisjunctive from each other, which means that there is no (or at leastno considerable) spectral overlap between the two sub-bands. It will beappreciated that for each additional cell layer, a dedicated additional“prioritized” sub-band will be added. In an exemplary networkimplementation with three cell layers, the available uplink transmissionbandwidth will thus be split in three sub-bands, and so on.

In one of its aspects the technology disclosed herein concerns a methodof operating a heterogeneous radio access network, such as thatillustrated by way of example in FIG. 1-FIG. 6. FIG. 7 illustratesrepresentative, basic acts or steps performed in a generic mode of themethod. Act 7-1 comprises dividing a frequency bandwidth usable by theheterogeneous radio access network into a partitioned portion (which isless than the entire bandwidth). As simply illustrated in FIG. 8 andFIG. 9, the frequency bandwidth usable by the heterogeneous radio accessnetwork may be split (as indicated by broken line S) into pluralpartitions, e.g., first partition P1 and second partition P2 in theexample of FIG. 8 and FIG. 9. As noted above, a partition or partitionedportion may be a subset (e.g., one or more frequencies or sub-carriers)of the frequency bandwidth usable by the heterogeneous radio accessnetwork. A partition plan (PP) describes the manner in which thefrequency bandwidth usable by the heterogeneous radio access network issplit into its plural partitions. The partition plan (PP) is distributedor otherwise provided to plural base station nodes of the heterogeneousradio access network 20, e.g., to the macro base station nodes and tothe micro base station nodes.

In one embodiment and mode illustrated by FIG. 8, act 7-1 may occur at acentral node or management node of the heterogeneous radio accessnetwork 20, such as management node 50 illustrated in FIG. 8. Forexample, in one example embodiment a frequency spectrum divider (e.g.,partitioner) 52 may be configured to divide the frequency bandwidthusable by the heterogeneous radio access network into the pluralpartitions based either on direct user input or by criteria from whichthe processor or computer determines how to create the partition planand thus how best to split or divide the frequency bandwidth. Thefrequency spectrum divider or partitioner 52 of the management node 50may be implemented by a processor or computer of management node 50. Insuch example embodiment wherein the management node 50 divides thefrequency bandwidth, the partition plan may be downloaded from themanagement node 50 to the plural base stations of the heterogeneousradio access network 20 as depicted by arrows D in FIG. 8.

In another embodiment and mode illustrated by FIG. 9, the act 7-1 ofdividing the frequency bandwidth usable by the heterogeneous radioaccess network into a partitioned portion comprises loading thepartition plan into the base station nodes of the heterogeneous radioaccess network 20. In other words, the pre-configured partition plan maybe stored or loaded into the plural base station nodes of theheterogeneous radio access network 20, either by downloading or other(e.g., direct) input into the scheduler 36 of the plural base stationnodes.

Act 7-2 and act 7-3 are primarily performed by base station nodes of theheterogeneous radio access network 20. Act 7-2, which may be performedby a scheduler 36 of a micro base station node, comprises assigning afrequency of the partitioned portion to a wireless terminal in an edgeregion of the micro cell. Act 7-3 may be performed by a micro basestation node of the heterogeneous radio access network 20. Act 7-3comprises assigning a frequency of the frequency bandwidth to a wirelessterminal which is in a center region of the micro cell. The assigning offrequencies to wireless terminals in the center region of a micro cellis performed by the micro base station which serves the wirelessterminal. The frequency assignment to a wireless terminal is in a centerportion of a cell may be by different criteria than that of a wirelessterminal in an edge portion of the cell. For example, the micro basestation may assign a frequency of the frequency bandwidth without regardto the partitioned portion (e.g., at any suitable frequency in thefrequency bandwidth without constraint of the partitioned portion) ifthe wireless terminal is in a center portion of the micro cell.

FIG. 7A illustrates an enhanced version of the method of FIG. 7 whichincludes act 7-4, in addition to act 7-1, act 7-2, and act 7-3. Act 7-4comprises assigning a frequency of the frequency bandwidth if the cellserved by the base station node is a macro cell and the wirelessterminal is in a center portion of the macro cell or does notsubstantially interfere with a micro cell. The assigning of frequenciesto wireless terminals which are at least within a center region of themacro cell is performed by a scheduler 36 of the macro base station nodewhich serves the wireless terminal. For example, for act 7-4 thefrequency may be assigned by different critiera, e.g., without regard tothe partitioned portion, so that the assignment may be essentiallyanywhere within the frequency bandwidth without being limited to thepartitioned portion.

The phraseology “at least within a center region” is employed so that itwill be understood that the generic method of FIG. 7 covers someembodiments in which only wireless terminals in the center region areactually assigned frequencies without regard to the partitioning (e.g.,assigned any frequency of the entire frequency bandwidth usable by theheterogeneous radio access network), and also covers some embodiments inwhich not only are wireless terminals in the center region are actuallyassigned frequencies without regard to the partitioning, but wirelessterminals in other regions of the cell (e.g., even in an edge region ofthe cell) may be assigned frequencies without regard to thepartitioning.

FIG. 7B shows a more detailed mode of the basic method of FIG. 7. TheFIG. 7B mode further includes performance of act 7-1B, preferably priorto act 7-2. Act 7-1B is performed by a base station node of theheterogeneous radio access network 20 (either a macro base station nodeor a micro base station node). Act 7-1B may be performed for eachwireless terminal in the heterogeneous radio access network, and foreach wireless terminal is performed by the base station of the servingcell for the wireless terminal. Act 7-1B comprises determining whetherthe wireless terminal is in the center region or the edge region of themicro cell. The terminal locator 34 of the base station may make thedetermination of act 7-1B based on, e.g., measurements received from thewireless terminal. In other respects the mode of FIG. 7B resembles thebasic mode of FIG. 7, including act 7-1, act 7-2, and act 7-3.

FIG. 7C shows another more detailed mode of the basic method of FIG. 7.In the FIG. 7C mode, act 7-1(C) comprises dividing the frequencybandwidth usable by the heterogeneous radio access network into pluralpartitioned portions (each of which is less than the entire bandwidth).The division of the frequency bandwidth into partitions is understoodfrom the preceding discussion of FIG. 8, and can be performed by acontrol or management node of the heterogeneous radio access network 20or by loading a pre-configured partition plan into the base stationnodes of the heterogeneous radio access network 20.

Act 7-2(C) comprises assigning frequencies from the partitioned portionsto wireless terminals in an edge region of the macro cell and wirelessterminals in an edge region of the micro cell. Act 7-2(C) is performedby a scheduler 36 of a micro base station node for wireless terminals inan edge region of a micro cell, and is performed by a scheduler 36 of amacro base station for wireless terminals in an edge region of a macrocell. In being assigned a frequency from a partitioned portion, thewireless terminal is not able to be assigned a frequency from the entirefrequency bandwidth without regard to partitioning. In other words, thefrequency assignment for the wireless terminal is restricted to one ofthe plural partitions and thus the entire frequency spectrum is noteligible for assignment.

As in the generic method, act 7-3 comprises assigning a frequency of thefrequency bandwidth to a wireless terminal which is in a center regionof the micro cell or at least within a center region of the macro cell.In some example embodiments the assignment of act 7-3 may be withoutregard to the partitioned portion(s).

The FIG. 7C mode is also illustrated and amplified by various examplemodes and embodiments described below.

It will be appreciated that the enhancement of act 7-4 of FIG. 7A mayalso be performed in conjunction with the methods of FIG. 7B and FIG.7C.

The basic method of FIG. 7, and the additional methods of FIG. 7A, FIG.7B, and FIG. 7C, are illustrated and amplified by the resourceallocation strategies of the various example modes and embodimentsdescribed below.

FIG. 10A illustrates a resource allocation strategy in which (like inthe generic method of FIG. 7) “cell center” wireless terminals, whetherin the center of a macro cell or the center of a micro cell, areassigned to any frequency of the frequency band (e.g., are assigned afrequency, e.g., without regard to the partitioning of the partitionplan). FIG. 10A further shows that wireless terminals in an edge regionE of a macro cell and wireless terminals in an edge region E of a microcell are assigned to separate frequency partitions to minimizeinterference between the micro cell wireless terminals and the wirelessterminals in the edge region E of a macro cell.

Thus, in the example embodiment illustrated in FIG. 10A the scheduler 36of a macro base station node is configured to assign a frequency from afirst partition (the left partition of FIG. 10A) to the wirelessterminal which it serves if the wireless terminal is in an edge regionof a macro cell served by the macro base station node. For example, thescheduler 36 of macro base station node 24 ₁ assigns a frequency fromthe first partition (the left partition of FIG. 10A) to the wirelessterminal in edge region 54 ₁.

On the other hand, the scheduler 36 of a micro base station node isconfigured to assign a frequency from the second partition (the rightpartition of FIG. 9) to the wireless terminal which it serves if thewireless terminal is in an edge region of a micro cell served by themicro base station node.

It so happens in the example embodiment of FIG. 10A that plural basestation nodes assign frequencies from the same partition (the leftpartition of FIG. 10A) to wireless terminals in their edge regions 54.For example, macro base station 24 ₁ assigns frequencies from the leftpartition of FIG. 10A to wireless terminals in edge region 54 ₁; macrobase station 24 ₂ assigns frequencies from the left partition of FIG.10A to wireless terminals in edge region 54 ₂; and so forth. Similarly,all micro base stations, regardless of in which macro cell they reside,assign frequencies from the right partition of FIG. 10A to wirelessterminals in their respective edge regions.

FIG. 10B shows example, representative acts or steps involved in amethod of operating a heterogeneous radio access network in accordancewith the strategy of FIG. 10A. Act 7-1(9) comprises dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions. Act 7-2.1(10) comprises assigning a frequencyfrom a first partition to wireless terminal(s) in an edge region of themacro cell served by the macro base station which performs the act. Act7-2.1(10) is performed by a scheduler 36 of the macro cell served by themacro base station which performs the act. Act 7-2.2(10) comprisesassigning a frequency from a second partition to wireless terminal(s) inan edge region of the micro cell. Act 7-2.2(10) is performed by ascheduler 36 of the micro cell served by the micro base station whichperforms the act. As in the basic method, act 7-3 comprises assigning afrequency of the frequency bandwidth to a wireless terminal which is ina center region of the micro cell or at least within a center region ofthe macro cell.

FIG. 11A and FIG. 12A illustrate two additional embodiments in whichfractional frequency reuse (FFR) is applied both within a macro cell forcell center and cell edge users, as well as between the micro cells.FIG. 11A and FIG. 12A thus illustrate other resource allocationstrategies, and particularly strategies in which the scheduler 36 of amacro base station is configured to assign a frequency from a selectedone of plural partitions of the frequency bandwidth if the wirelessterminal is in an edge region of the cell served by the macro basestation node. The selected one of the plural partitions is a differentpartition than that which is used by another base station node servingan adjacent macro cell to assign a frequency to another wirelessterminal in an edge region of the adjacent macro cell. Moreover, theselected one of the plural partitions may be a different partition thanthat which is used by a micro base station node within the macro cell toassign a frequency to any wireless terminal within the micro basestation node.

FIG. 11B shows example, representative acts or steps involved in amethod of operating a heterogeneous radio access network which issuitable for the strategy of FIG. 11A. Act 7-1(9) comprises dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions. In the particular situation of FIG. 11A and FIG.11B, the frequency bandwidth usable by the heterogeneous radio accessnetwork is divided into four partitions.

Act 7-2.1(11) comprises assigning a frequency from a first partition towireless terminals in the edge region of a first macro cell. Act7-2.1(11) is performed by a scheduler 36 of the macro base station ofthe first macro cell, for example macro base station 24 _(k). Act7-2.2(11) comprises assigning a frequency from a second partition to awireless terminal in the edge region of a second macro cell. Act7-2.1(11) is performed by a scheduler 36 of the macro base station ofthe second macro cell, for example macro base station 24 ₂. Act7-2.3(11) comprises assigning a frequency from a third partition to awireless terminal in the edge region of a micro cell. As in the basicmethod, act 7-3 comprises assigning a frequency of the frequencybandwidth to a wireless terminal which is in a center region of themicro cell or at least within a center region of the macro cell.

FIG. 11C shows example, representative acts or steps involved in analternate method of operating a heterogeneous radio access network whichis suitable for the strategy of FIG. 11A. The method of FIG. 11C differsfrom the method of FIG. 11B by replacing act 7-2.3(11) with act7-2.3′(11). Act 7-2.3′(11) comprises assigning the frequency from thethird partition to the wireless terminal in the edge region of a microcell regardless of whether the micro cell is in the first macro cell orthe second macro cell. Act 7-3 comprises assigning a frequency of thefrequency bandwidth to a wireless terminal which is in a center regionof the micro cell or at least within a center region of the macro cell.

In the resource allocation strategy of FIG. 12A, the selected one of theplural partitions may be a same partition that is used by a micro basestation node within another macro cell to assign a frequency to awireless terminal in an edge region of the micro base station node whichis in the another macro cell. In this regard, FIG. 12B shows example,representative acts or steps involved in a method of operating aheterogeneous radio access network which is suitable for the strategy ofFIG. 12A. The first three acts of FIG. 12B are similar to those of FIG.11B. In particular, act 7-1(11) of FIG. 11B comprises dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions. Act 7-2.1(11) comprises assigning a frequencyfrom a first partition to a wireless terminal in an edge region of afirst macro cell. Act 7-2.2(11) comprises assigning a frequency from asecond partition to a wireless terminal in an edge region of a secondmacro cell. Act 7-2.3(12) comprises assigning a frequency from a thirdpartition to a wireless terminal in an edge region of a first micro cellwithin the first macro cell. Act 7-2.3(12) comprises assigning afrequency from a fourth partition to a wireless terminal in an edgeregion of a second micro cell within the first macro cell. Act 7-3comprises assigning a frequency of the frequency bandwidth to a wirelessterminal which is in a center region of the micro cell or at leastwithin a center region of the macro cell.

FIG. 12C shows example, representative acts or steps involved in analternate method of operating a heterogeneous radio access network whichis suitable for the strategy of FIG. 12A. The method of FIG. 12C differsfrom the method of FIG. 12B by inclusion of act 7-2.3.1(12) and act7-2.4.1(12), which follow act 7-2.3(12) and act 7-2.4(12), respectively.Act 7-2.3.1(12) comprises assigning a frequency from the third partitionto a wireless terminal in an edge region of a first micro cell withinthe second macro cell. Act 7-2.4.1(12) comprises assigning a frequencyfrom the fourth partition to a wireless terminal in an edge region of asecond micro cell within the second macro cell.

FIG. 13A illustrates an embodiment and mode of the heterogeneousfraction frequency reuse (FFR) technique of the technology disclosedherein in which macro cells employ a traditional N=1 frequencyassignment while a rate ⅓ FFR scheme is applied to the micro cells basedon the macro cells in which the micro cells reside. The illustration ofFIG. 13A employs two micro cells per macro cell, however the technologymay be applied to an arbitrary number of micro cells per macro cell (notnecessarily the same) and an arbitrary fraction frequency reuse (FFR)rate.

In accordance with the embodiment and mode of FIG. 13A, the scheduler 36of a micro base station is configured to assign, to a wireless terminalin an edge region of its micro cell, a frequency from a selected one ofplural partitions of the frequency bandwidth. The selected one of theplural partitions is a same partition which is used, by another basestation node serving another micro cell in a same macro cell, to assigna frequency to another wireless terminal in an edge region of theanother micro cell. But the selected one of the plural partitions isdifferent from another partition which is used, by yet another basestation node serving another micro cell in another macro cell which isadjacent to the macro cell, to assign a frequency to yet anotherwireless terminal in an edge region of the yet another micro cell.

FIG. 13B shows example, representative acts or steps involved in amethod of operating a heterogeneous radio access network which issuitable for the strategy of FIG. 13A. Act 7-1 comprises dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions. Act 7-2.1(13) comprises assigning a frequency ofa first partition to wireless terminals in an edge region of the pluralmicro cells within a first macro cell. Act 7-2.2(13) comprises assigninga frequency of a second partition to wireless terminals in an edgeregion of the plural micro cells within a second macro cell. Act 7-3comprises assigning a frequency of the frequency bandwidth to a wirelessterminal which is in a center region of the micro cell or at leastwithin a center region of the macro cell.

FIG. 13C shows example, representative acts or steps involved in analternate method of operating a heterogeneous radio access network whichis suitable for the strategy of FIG. 13A. The method of FIG. 13C differsfrom the method of FIG. 13B by virtue of substitution of act 7-3(13) foract 7-3. Act 7-3(13) comprises assigning a frequency of the frequencybandwidth to a wireless terminal which is in any of the plural macrocells (without regard to where in the macro cells) or in the centerregion of any of the plural micro cells.

FIG. 14A illustrates an embodiment and mode in which the macro cellsagain use an N=1 deployment, but the fraction frequency reuse (FFR)scheme may be applied across the micro cells within each macro cell. Themicro-cell fraction frequency reuse (FFR) assignments are staggeredbetween micro cells across macro cell boundaries to ensure that no twoneighboring micro-cells share the same fraction frequency reuse (FFR)partition.

In accordance with the resource allocation strategy of FIG. 14A, thescheduler 36 of a micro base station is configured to assign (to awireless terminal in its edge region) a frequency from a selected one ofplural partitions of the frequency bandwidth. The selected one of theplural partitions is a different partition than that which is used, byanother base station node serving another micro cell in a same macrocell, to assign a frequency to another wireless terminal in an edgeregion of the another micro cell.

FIG. 14B shows example, representative acts or steps involved in amethod of operating a heterogeneous radio access network which issuitable for the strategy of FIG. 14A. Act 7-1 comprises dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions. Act 7-2.1(14) comprises assigning a frequency ofa first partition to a wireless terminal in an edge region of a firstmicro cell within a first macro cell. Act 7-2.1(14) comprises assigninga frequency of a second partition to a wireless terminal in an edgeregion of a second micro cell within the first macro cell. Act 7-3comprises assigning a frequency of the frequency bandwidth to a wirelessterminal which is in a center region of the micro cell or at leastwithin a center region of the macro cell.

FIG. 14C shows example, representative acts or steps involved in analternate method of operating a heterogeneous radio access network whichis suitable for the strategy of FIG. 14A. The method of FIG. 14C differsfrom the method of FIG. 14B by inclusion of act 7-2.1.1(14) and act7-2.2.1(14), which follow act 7-2.1(14) and act 7-2.2(14), respectively.Act 7-2.1.1(14) comprises assigning a frequency of the first partitionto a wireless terminal in an edge region of a first micro cell within asecond macro cell. Act 7-2.2.1(14) comprises assigning a frequency ofthe second partition to a wireless terminal in an edge region of asecond micro cell within the second macro cell.

In some example embodiments and/or modes, known as sub-partitionedembodiments and/or modes, the frequency bandwidth usable by theheterogeneous radio access network is divided into plural partitions andthe plural partitions are further divided into plural sub-partitions.Some example sub-partitioned embodiments and/or modes involve multiplestages of partitioning. For example, some example embodiments and modesinvolve two stages of partitioning. A first partition is associated withthe plural macro cells and a second partition is primarily (but notnecessarily exclusively) associated with the plural micro cells.

Two example sub-partitioned embodiments and/or modes are illustrated inFIG. 15 and FIG. 16. Both FIG. 15 and FIG. 16 show the frequencybandwidth usable by the heterogeneous radio access network being dividedinto a first partition B1 and a second partition B2, and further showthat the first partition B1 is sub-divided into sub-partitions B11, B12,and B13 and that the second partition B2 is sub-divided intosub-partitions B21, B22, and B23. FIG. 15 shows that first partition B1is a sub-band for interfering macro UEs or macro cell edge UEs, whilethe second partition B2 is for, e.g., micro cell edge UEs. FIG. 16 showsthat the first partition B1 is a reserved sub-band of macro base stationBS1, while the second partition B2 is a reserved sub-band of pico (e.g.,micro) base stations.

In the FIG. 15 embodiment and mode a two stage bandwidth partitioning isemployed with four sub-bands employed for the macro-cell UEs. Theapproach of FIG. 15 addresses, e.g., the asymmetrical interferencebetween the macro and micro-cells of the heterogeneous network. Incombination with a PFTF (proportional fair in time and frequency)scheduling of the UEs, the embodiment of FIG. 15 achieves both aninterference reduction and SINR improvement for the micro cell userswhile maintaining the macro cell SINR levels.

In a heterogeneous deployment, the set of transceiver devices sensitiveto interference may not correspond to the set of transceiver devicescausing strong inter-cell interference. As an example, transceiverdevices served in micro cells and sensitive to interference are notnecessarily causing much interference to transceiver devices that areserved in adjacent or overlapping macro cells and sensitive tointerference. In a similar manner, transceiver devices served in a macrocell and close to the border of a micro cell may not necessarily be theones that cause the strongest interference in the micro cell.

In the uplink (UL) of a heterogeneous radio access network 20 (HetNet)such as that illustrated in FIG. 15, an interfering macro wirelessterminal (UE) is not necessarily the same as a cell-edge macro wirelessterminal (UE). A macro wireless terminal interfering with theneighboring macro base station is usually located at the edges of itsserving macro cell. A macro wireless terminal interfering with a microbase station located within the same macro cell area of the consideredmacro wireless terminal has a low pathloss (e.g., short distance) to themicro base station and a large pathloss to the macro base station.Cell-edge macro wireless terminals have a large pathloss to theirserving base station but not all of them are close to the micro basestation. There may be macro wireless terminals interfering with themicro base station in the uplink (UL) and that are usually notcategorized as cell-edge wireless terminals. The hatched region in FIG.15A shows a region where the macro wireless terminals of macro basestation 24 _(i) which potentially strongly interfere with micro cell 28_(i-1) may be located.

The resulting throughput gains achieved by the two stage bandwidthpartitioning of FIG. 15 for 50% RB utilization and FTP traffic aresummarized in FIG. 21A, FIG. 21B, FIG. 22, and Table 1 and Table 2.Table 1 is associated with FIG. 21A and FIG. 21B; Table 2 is associatedwith FIG. 22. It can be seen that these gains can be over 30% in eitherthe mean or five percentile throughput, depending on the application

While some of the embodiments and modes described herein primarilyconcern vertical inter-cell interference coordination (ICIC) betweencells of different layers, other embodiments such as that shown in FIG.16 combine such vertical ICIC with horizontal ICIC between cells of thesame layer.

FIG. 16 illustrates for the network scenario of FIG. 16A an exemplarybandwidth partitioning scheme (in accordance with FIG. 3A) for macrolayer ICIC. It will be appreciated that a similar approach could beimplemented for micro (e.g., pico) layer ICIC. As shown in FIG. 16, thetotal bandwidth is split into two partitions or sub-bands (B1, B2)depicted by broad columns in FIG. 16. These partitions or sub-bands maybe identical to that illustrated in FIG. 3A. For the exemplary case ofthree adjacent macro cells as shown in FIG. 16, each partition/sub-bandB1, B2 is further split into three sub-partitions B11, B12, B13, B21,B22, B23. It should be noted that the relative sizes of thesesub-partitions are not necessarily to scale.

In one exemplary assignment scenario for FIG. 16, the wireless terminalsare first assigned to one of the sub-bands B1, B2 according to anysuitable vertical ICIC technique including those described herein. In anext step, each macro wireless terminal is further assigned to one ofthe various partitions B11 to B23 according to any conventional verticalICIC technique. It should be noted that a combined vertical/horizontalICIC procedure can also be performed for terminals served in the microcells (e.g., pico cells). Since micro cells are often sufficientlyisolated from each other, this option has not been illustrated in FIG.16.

FIG. 17 shows example, representative acts or steps involved in ageneric method of operating a heterogeneous radio access network inaccordance with the sub-partitioned embodiments and/or modes of thetechnology disclosed herein. Act 7-1(17) comprises dividing thefrequency bandwidth usable by the heterogeneous radio access networkinto plural partitions including a first partition (e.g., partition B1)and a second partition (partition B2). Act 7-1.1(17) comprises dividingthe plural partitions into plural sub-partitions. Act 7-2.1(17) and act7-2.2(17) collectively essentially correspond to generic act 7-2, theact of assigning a frequency of a partitioned portion (e.g., the secondpartition) to a wireless terminal in an edge region a micro cell. Act7-2.1(17) comprises assigning a frequency of a first sub-partition ofthe second partition if the wireless terminal is in an edge region of amicro cell in the first macro cell. Act 7-2.1(17) comprises assigning afrequency of a second sub-partition of the second partition if thewireless terminal is in an edge region of a micro cell in the secondmacro cell. Act 7-3 comprises assigning a frequency of the frequencybandwidth to a wireless terminal which is in a center region of themicro cell or at least within a center region of the macro cell.

Both act 7-2.1(17) and act 7-2.2(17) are performed by schedulers ofmicro base stations, but are performed by schedulers of different microbase stations. For example, in the embodiment of FIG. 15 act 7-2.1(17)may be performed by micro base station of micro cell 28 ₁₋₁ assigning afrequency of sub-partition B21 (since micro cell 28 ₁₋₁ is in macro cell22 ₁), while act 7-2.2(17) may be performed by micro base station ofmicro cell 28 ₂₋₁ assigning a frequency of sub-partition B22 (sincemicro cell 28 ₂₋₁ is in macro cell 22 ₂). Further it will be appreciatedthat other acts are also encompassed by the generic method of FIG. 17,such as a third micro base station (e.g., a micro base station of microcell 28 ₃₋₁) assigning a frequency of a third sub-partition (e.g.,sub-partition B23) of the second partition if the wireless terminal isin an edge region of micro cell 28 ₃₋₁, the micro cell 28 ₃₋₁ being inthird macro cell 22 ₃.

In the embodiment of FIG. 15 and in accordance with the method of FIG.17, the scheduler 36 of a particular macro base station of a macro cellwhich comprises the heterogeneous radio access network assigns, to awireless terminal served by the particular macro cell, a frequency of aselected one of the sub-partitions of the first partition if thewireless terminal is in an edge region of the particular macro cell orif the wireless terminal substantially interferes with a cell other thanthe particular macro cell. For example, in the context of FIG. 15 themacro base station 24 ₁ would assign a frequency from sub-partition B11to a wireless terminal which either is in an edge region 54 ₁ of theparticular macro cell or which substantially interferes with a cellother than the particular macro cell. The selected sub-partition of thefirst partition which is assigned may be a sub-partition associated withthe particular macro cell. For example, in FIG. 15 the sub-partition B11may be associated with macro cell 22 ₁ and thus used by the scheduler 36of macro base station 24 ₁ for assigning frequencies to macro edge andinterfering wireless terminals. The scheduler 36 of the particular macrocell assigns frequencies to any center region wireless terminal ornon-interfering wireless terminal, and in some embodiments may do sowithout regard to partitioning (e.g. any frequency of the entire usablebandwidth).

FIG. 17A shows basic, representative acts or steps involved in asub-partitioning resource assignment strategy in which macro basestations assign frequencies in a first partition to wireless terminalswhich are in their respective edge regions. The method of FIG. 17Aincludes the acts 7-1(17), 7-1.1(17), 7-2.1(17), 7-2.2(17), and 7-3 ofFIG. 17, as well as further acts 7-2.3(17A) and 7-2.4(17A). Act7-2.3(17A) comprises assigning a frequency of a first sub-partition ofthe first partition if the wireless terminal is in an edge region of afirst macro cell. Act 7-2.4(17A) comprises assigning a frequency of asecond sub-partition of the first partition if the wireless terminal isin an edge region of a second macro cell. Act 7-2.3(17A) is performed bya scheduler 36 of a macro base station, such as the scheduler 36 of basestation 24 ₁ which uses the first sub-partition B11 to assignfrequencies to wireless terminals in edge region 54 ₁. Act 7-2.4(17A) isperformed by a scheduler 36 of another macro base station, such as thescheduler 36 of base station 24 ₂ which uses the second sub-partitionB12 to assign frequencies to wireless terminals in edge region 54 ₂.

FIG. 17B shows basic, representative acts or steps involved in asub-partitioning resource assignment strategy in which macro basestations assign frequencies in a first partition to wireless terminalswhich interfere with other cells, e.g., interfering UEs. The method ofFIG. 17B is germane, e.g., to the embodiment and mode of FIG. 16. Themethod of FIG. 17B includes the acts 7-1(17), 7-1.1(17), 7-2.1(17),7-2.2(17), and 7-3 of FIG. 17, as well as further acts 7-2.3(17B) and7-2.4(17B). Act 7-2.3(17B) comprises assigning a frequency of a firstsub-partition of the first partition if the wireless terminal is in afirst macro cell and interferes with any micro base station node. Act7-2.4(17B) comprises assigning a frequency of a second sub-partition ofthe first partition if the wireless terminal is in a second macro celland interferes with any micro base station node. Act 7-2.3(17B) isperformed by a scheduler 36 of a macro base station, such as thescheduler 36 of base station 24 ₁ which uses the first sub-partition B11to assign frequencies to interfering wireless terminals served by basestation 24 ₁. Act 7-2.4(17B) is performed by a scheduler 36 of anothermacro base station, such as the scheduler 36 of base station 24 ₂ whichuses the second sub-partition B12 to assign frequencies to interferingwireless terminals served by base station 24 ₂.

FIG. 17C shows basic, representative acts or steps involved in asub-partitioning resource assignment strategy in which macro basestations may assign frequencies in the second partition to wirelessterminals which do not interfere with other cells, e.g., non-interferingUEs. The method of FIG. 17C includes the acts 7-1(17), 7-1.1(17),7-2.1(17), 7-2.2(17), and 7-3 of FIG. 17, as well as further act7-2.3(17C). In the method of FIG. 17C, a wireless terminal, served by amacro cell, may be assigned a frequency of the frequency bandwidthusable by the heterogeneous radio access network (e.g., without regardto partitioning) if the wireless terminal does not substantiallyinterfere with a cell other than the particular macro cell. Asillustrated in FIG. 17C, act 7-2.3(17C) particularly comprises assigninga frequency of the second partition to a wireless terminal in one of theplural macro cells if the wireless terminal is in a macro cell and doesnot substantially interfere with any micro base station node. Act7-2.3(17C) is performed by a scheduler 36 of a macro base station whichserves the non-interfering wireless terminal.

FIG. 17D shows basic, representative acts or steps involved in asub-partitioning resource assignment strategy in which macro basestations may assign frequencies in the second partition to wirelessterminals which do not interfere with any micro base station node. Themethod of FIG. 17D includes the acts 7-1(17), 7-1.1(17), 7-2.1(17),7-2.2(17), and 7-3 of FIG. 17, as well as further act 7-2.3(17D) and act7-2.4(17D). In the method of FIG. 17D, a wireless terminal, served byany one of the plural macro cells, may be assigned a frequency of thesecond partition if the wireless does not substantially interfere withany micro base station node. In this regard, act 7-2.3(17D) comprisesassigning a frequency of a first sub-partition of the second partitionif the wireless terminal is in a first macro cell and does notsubstantially interfere with any micro base station node. Act 7-2.4(17D)comprises assigning a frequency of a second sub-partition of the secondpartition if the wireless terminal is in a second macro cell and doesnot substantially interfere with any micro base station node. Forexample, in the context of FIG. 15, the scheduler 36 of macro basestation 24 ₁ may assign a frequency of partition B21 to a wirelessterminal served by macro base station 24 ₁ that does not substantiallyinterfere with any micro base station node. Similarly, the scheduler 36of macro base station 24 ₂ may assign a frequency of partition B22 to awireless terminal served by macro base station 24 ₂ that does notsubstantially interfere with any micro base station node.

As evident from the preceding, a scheduler of a macro base station maybe configured to assign, to a wireless terminal that it serves, afrequency of a selected one of the sub-partitions of the secondpartition, and the selected one of the sub-partitions of the secondpartition may be associated with the particular macro cell. For example,in conjunction with non-interfering wireless terminals and in thecontext of FIG. 15, sub-partition B21 may be associated with macro cell22 ₁ and macro base station 24 ₁; sub-partition B22 may be associatedwith macro cell 22 ₂ and macro base station 24 ₂; and sub-partition B23may be associated with macro cell 22 ₃ and macro base station 24 ₃.

In another example sub-partitioned embodiment wherein the base stationnode serves a particular macro cell comprising the plural macro cells,the scheduler of a particularly macro base station node may beconfigured to assign, to a wireless terminal that it serves, a frequencyof the second partition if the wireless terminal substantiallyinterferes with a macro cell other than the particular macro cell anddoes not substantially interfere with a micro cell.

What constitutes “substantial interference” may be determined relativeto a threshold, such as a predetermined threshold. For example, thereceived power of a user A (e.g., wireless terminal) at a cell B may beused to determine if user a substantially interferes with cell B. It maybe decided that substantial interference occurs if the received powerfrom user A is larger than a predetermined threshold or among thehighest received power signals from all users.

As reflected by acts such as act 7-2.1(17) and act 7-2.1(17), for thesub-partitioning embodiments the scheduler 36 of a micro base stationnode may be configured to assign to the wireless terminal a frequencyselected from a selected sub-partition of the second partition if thewireless terminal is in an edge region of the particular micro cell. Inan example implementation, the selected sub-partition of the secondpartition may be associated with the macro cell in which the particularmicro cell is located. For example, in the context of FIG. 15,sub-partition B21 may be associated with micro cell 28 ₁₋₁ and/or microcell 28 ₁₋₂; sub-partition B22 may be associated with micro cell 28 ₂₋₁and/or micro cell 28 ₂₋₂; and sub-partition B23 may be associated withmicro cell 28 ₃₋₁ and/or micro cell 28 ₃₋₂.

In an example embodiment and mode, the frequency bandwidth the firstsub-partition of the first partition is separated from the firstsub-partition of the second partition by at least the secondsub-partition of the first partition. For example, in the context ofFIG. 15, sub-partition B11 is separated from sub-partition B21 by atleast sub-partition B12 (and, in fact, also by sub-partition B13).

Typically a base station BS comprises units or functionalities otherthan those shown in FIG. 4, some of which are illustrated in FIG. 18.Among such other units or functionalities are communications interface60 (to other nodes of the radio access network (RAN) or core networknodes); frame handler 62 (for frames or sub-frames communicated overinterface 38 and thus the radio interface); frame handler 64 (for framesor sub-frames communicated by communications interface 60 between thebase station BS and other nodes); signal handler 66; schedulerconfigurator 68; signal handler 70; data handler 70 and data handler 72,and applications 74. The frame handler 64 connects to signal handler 66and data handler 70, while frame handler 62 connects to signal handler70 and data handler 72.

In example embodiments, functionalities of a base station may berealized using electronic circuitry. For example, FIG. 18 shows anembodiment of an example base station BS wherein the scheduler 36 andother functionalities are realized by electronic circuitry andparticularly by platform 90, the platform 90 being framed by brokenlines in FIG. 18. The terminology “platform” is a way of describing howthe functional units of the base station node can be implemented orrealized by machine including electronic circuitry. One example platform90 is a computer implementation wherein one or more of the framedelements including scheduler 36 are realized by one or more processors92 which execute coded instructions and which use non-transitory signalsin order to perform the various acts described herein. In such acomputer implementation the scheduler 36 can comprise, in addition to aprocessor(s), memory section 93 (which in turn can comprise randomaccess memory 94; read only memory 95; application memory 96 (whichstores, e.g., coded instructions which can be executed by the processorto perform acts described herein); and any other memory such as cachememory, for example.

Typically the platform 90 of base station BS also comprises otherinput/output units or functionalities, some of which are illustrated inFIG. 18, such as keypad 100; audio input device 102 (e.g. microphone);visual input device 104 (e.g., camera); visual output device 106; andaudio output device 108 (e.g., speaker). Other types of input/outputdevices can also be connected to or comprise base station BS.

In the example of FIG. 18 the platform 90 has been illustrated ascomputer-implemented or computer-based platforms. Another exampleplatform suitable for the packet core network entity in particular isthat of a hardware circuit, e.g., an application specific integratedcircuit (ASIC) wherein circuit elements are structured and operated toperform the various acts described herein.

As explained with reference to FIG. 8, in some example embodiments andmodes a partition plan may be downloaded from a management node 50 orthe like to the scheduler 36 of a base station BS. Such downloadedpartition plan may be carried by signals which are applied to basestation BS over communication interface 60 and which are routed tosignal handler 66. The signal handler 66 in turn provides the partitionplan-bearing signals to scheduler configurator 68. The schedulerconfigurator 68 in turn provides or programs the partition plan intoscheduler 36.

In another embodiment as exemplified by FIG. 9, the partition plan mayinstead or additionally be installed into the scheduler 36 through meansother than a network download. For example, the partition plan may beinput to scheduler 36 more directly, e.g., through memory 93 (e.g., apartition plan stored in ROM 95 or RAM 94) or an input device of theinput/output section (such as keypad 100).

Typically a wireless terminal (UE) 30 also comprises units orfunctionalities other than those shown in FIG. 5. Some such otherfunctionalities or units are illustrated in FIG. 19. Among such otherunits or functionalities are scheduler 136; frame handler 162 (forframes or sub-frames communicated over interface 44 and thus the radiointerface); signal handler 170; data handler 172, and applications 174.The frame handler 164 connects to signal handler 170 and data handler70, while frame handler 62 connects to signal handler 170 and datahandler 172.

In example embodiments, functionalities of a base station may berealized using electronic circuitry. For example, FIG. 19 shows anembodiment wherein many functionalities of an example wireless terminal(UE) 30 are realized by electronic circuitry and particularly byplatform 190, the platform 190 being framed by broken lines in FIG. 18.The terminology “platform” is a way of describing how the functionalunits of the wireless terminal (UE) 30 may be implemented or realized bymachine including electronic circuitry. One example platform 190 is acomputer implementation wherein one or more of the framed elements arerealized by one or more processors 192 which execute coded instructionsand which use non-transitory signals in order to perform the variousacts described herein. In such a computer implementation the framefunctionalities may comprise, in addition to a processor(s), memorysection 193 (which in turn can comprise random access memory 194; readonly memory 195; application memory 196 (which stores, e.g., codedinstructions which can be executed by the processor to perform actsdescribed herein); and any other memory such as cache memory, forexample.

Typically the platform 190 of wireless terminal (UE) 30 also comprisesother input/output units or functionalities, some of which areillustrated in FIG. 19, such as keypad 200; audio input device 202 (e.g.microphone); visual input device 204 (e.g., camera); visual outputdevice 206; and audio output device 208 (e.g., speaker). Other types ofinput/output devices can also be connected to or comprise base stationBS.

In the example of FIG. 19 the platform 190 has been illustrated ascomputer-implemented or computer-based platforms. Another exampleplatform suitable for the framed functionalities, in particular is thatof a hardware circuit, e.g., an application specific integrated circuit(ASIC) wherein circuit elements are structured and operated to performthe various acts described herein.

As used herein, a “wireless terminal” can be a mobile station or userequipment unit (UE) such as a mobile telephone (“cellular” telephone) ora laptop with wireless capability (e.g., mobile termination), and thuscan be, for example, a portable, pocket, hand-held, computer-included,or car-mounted mobile devices which communicates voice and/or data via aradio access network. Moreover, a wireless terminal can be a fixedterminal which communicates voice and/or data via a radio accessnetwork.

An examplary criterion to identify cell-edge transceiver devices iscalled geometry. The geometry G_(u) of a transceiver device u served bya base station BS0 is given by

${G_{u} = \frac{{TxP}_{B\; S\; 0} \cdot {PL}_{{B\; S\; 0},u}}{{\sum\limits_{i \in {{S\backslash{BS}}\; 0}}{{TxP}_{i} \cdot {PL}_{i,u}}} + N}},$where S is the set of adjacent base stations, TxP is the transmit powerof the considered BS, PL is the pathloss from the transceiver device uto the considered base station, and N is the receiver noise power. Bysubjecting the geometry parameter derived for a particular transceiverdevice to, for example, a threshold decision, it can be determinedwhether or not the particular transceiver device is located at a celledge.

The technology disclosed herein has primarily been exemplified in thecontext of E-UTRAN and an evolved Packet core (EPC), e.g., LTE/SAE.However, the technology disclosed herein is not limited to anyparticular network or technology/generation, since the person skilled inthe art realize that the principles are applicable for other mobilesystems as well, such as cdma2000, which currently also uses locationarea lists.

Advantageously, the technology disclosed herein increases cell edgethroughput in heterogeneous interference limited environments whilemaintaining overall aggregate cell throughput.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. Thus the scope of this invention should be determinedby the appended claims and their legal equivalents. Therefore, it willbe appreciated that the scope of the present invention fully encompassesother embodiments which may become obvious to those skilled in the art,and that the scope of the present invention is accordingly to be limitedby nothing other than the appended claims, in which reference to anelement in the singular is not intended to mean “one and only one”unless explicitly so stated, but rather “one or more.” All structural,chemical, and functional equivalents to the elements of theabove-described preferred embodiment that are known to those of ordinaryskill in the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. Moreover, it is notnecessary for a device or method to address each and every problemsought to be solved by the present invention, for it to be encompassedby the present claims. Furthermore, no element, component, or methodstep in the present disclosure is intended to be dedicated to the publicregardless of whether the element, component, or method step isexplicitly recited in the claims. No claim element herein is to beconstrued under the provisions of 35 U.S.C. 112, sixth paragraph, unlessthe element is expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of operating a heterogeneous radioaccess network, the heterogeneous radio access network comprising amacro layer including at least one macro cell served by a macro basestation node and a micro layer comprising at least one micro cell servedby a micro base station node, the heterogeneous radio access networkcomprising plural macro cells and plural micro cells within each of theplural macro cells, the method comprising: dividing a frequencybandwidth usable by the heterogeneous radio access network into afrequency-partitioned portion which is less than the entire frequencybandwidth; assigning a frequency of the frequency-partitioned portion toa wireless terminal in an edge region of the micro cell; assigning afrequency of the frequency bandwidth to a wireless terminal which is ina center region of the micro cell or at least within a center region ofthe macro cell; dividing the frequency bandwidth usable by theheterogeneous radio access network into plural partitions including afirst partition and a second partition; dividing the plural partitionsinto plural sub-partitions; assigning a frequency of a second partitionto a wireless terminal in an edge region of one of the plural microcells by: assigning a frequency of a first sub-partition of the secondpartition if the wireless terminal is in an edge region of a micro cellin the first macro cell; and assigning a frequency of a secondsub-partition of the second partition if the wireless terminal is in anedge region of a micro cell in the second macro cell; assigning afrequency of a first partition to a wireless terminal in one of theplural macro cells by: assigning a frequency of a first sub-partition ofthe first partition if the wireless terminal is in a first macro celland interferes with any micro base station node; assigning a frequencyof a second sub-partition of the first partition if the wirelessterminal is in a second macro cell and interferes with any micro basestation node.
 2. The method of claim 1, wherein in the frequencybandwidth the first sub-partition of the first partition is separatedfrom the first sub-partition of the second partition by at least thesecond sub-partition of the first partition.
 3. A method of operating aheterogeneous radio access network, the heterogeneous radio accessnetwork comprising a macro layer including at least one macro cellserved by a macro base station node and a micro layer comprising atleast one micro cell served by a micro base station node, theheterogeneous radio access network comprising plural macro cells andplural micro cells within each of the plural macro cells, the methodcomprising: dividing a frequency bandwidth usable by the heterogeneousradio access network into a frequency-partitioned portion which is lessthan the entire frequency bandwidth; assigning a frequency of thefrequency-partitioned portion to a wireless terminal in an edge regionof the micro cell; assigning a frequency of the frequency bandwidth to awireless terminal which is in a center region of the micro cell or atleast within a center region of the macro cell; dividing the frequencybandwidth usable by the heterogeneous radio access network into pluralpartitions including a first partition and a second partition; dividingthe plural partitions into plural sub-partitions; assigning a frequencyof a second partition to a wireless terminal in and edge region of oneof the plural micro cells by: assigning a frequency of a firstsub-partition of the second partition if the wireless terminal is in anedge region of a micro cell in the second macro cell; and assigning afrequency of the second sub-partition of the second partition if thewireless terminal is in an edge region of a micro cell in the secondmacro cell; assigning a frequency of the second partition to a wirelessterminal in one of the plural macro cells if the wireless terminal is ina macro cell and does not substantially interfere with any micro basestation node.
 4. The method of claim 3, further comprising assigning afrequency of to the wireless terminal in one of the plural macro cellsby: assigning a frequency of a first sub-partition of the secondpartition if the wireless terminal is in a first macro cell and does notsubstantially interfere with any micro base station node; assigning afrequency of a second sub-partition of the second partition if thewireless terminal is in a second macro cell and does not substantiallyinterfere with any micro base station node.
 5. The method of claim 3,wherein in the frequency bandwidth the first sub-partition of the firstpartition is separated from the first sub-partition of the secondpartition by at least the second sub-partition of the first partition.6. A base station node of a heterogeneous radio access network, theheterogeneous radio access network comprising a macro layer including atleast one macro cell served by a macro base station node and a microlayer including at least one micro cell served by a micro base stationnode, wherein the heterogeneous radio access network comprises pluralmacro cells and plural micro cells within each of the plural macrocells, wherein a frequency bandwidth usable by the heterogeneous radioaccess network is divided into plural partitions and the pluralpartitions are divided into plural sub-partitions, wherein a firstpartition is associated with the plural macro cells and a secondpartition is associated with the plural micro cells, wherein the basestation node serves a particular macro cell comprising the plural macrocells, the base station node comprising: a terminal locator configuredto obtain an indication of location of a wireless terminal in a cellserved by the base station node; a scheduler configured to use theindication of location to assign to the wireless terminal a frequency ofthe frequency bandwidth usable by the heterogeneous radio accessnetwork, the scheduler being configured to assign a frequency from afrequency-partitioned portion of the frequency bandwidth if the wirelessterminal is in an edge region of the cell served by the base stationnode, the frequency-partitioned portion being less than the entirefrequency bandwidth, and wherein the scheduler is further configured toassign to the wireless terminal a frequency of the second partition ifthe wireless terminal substantially interferes with a macro cell otherthan the particular macro cell and does not substantially interfere witha micro cell.
 7. The base station node of claim 6, wherein the scheduleris further configured to assign to the wireless terminal a frequency ofa selected one of the sub-partitions of the second partition, andwherein the selected one of the sub-partitions of the second partitionis associated with the particular macro cell.